The Limits of Density

Density is all the rage these days. Urban economists, some of whom could be heard extolling the praises of "sun, skills, and sprawl" just a few years ago, now see increasing density as the key to improving productivity and driving economic growth. In his story for The Atlantic, "How Skyscrapers Can Save the City," Harvard University’s Edward Glaeser put it this way: "As America struggles to regain its economic footing, we would do well to remember that dense cities are also far more productive than suburbs, and offer better-paying jobs ... tall buildings enable the human interactions that are at the heart of economic innovation, and of progress itself." Well-intentioned planners and preservationists drive up prices when they stand in the way of taller and taller buildings, he argues. Overly restrictive height limitations not only impede economic progress, but make cities less, not more, liveable.

There can be no doubt that density has its advantages. In general, denser cities are more productive, more innovative, and more energy efficient. But only up to a point.

America’s high-tech, venture-funded start-up model of innovation came of age not in skyscraper canyons but in places like Silicon Valley

The key function of a city is to enable exchange, interaction, and the combination and recombination of people and ideas. When buildings become so massive that street life disappears, they can damp down and limit just this sort of interaction, creating the same isolation that is more commonly associated with sprawl. As Jane Jacobs aptly put it: "in the absence of a pedestrian scale, density can be big trouble." Skyscraper canyons of the sort that are found in many Asian mega-cities, and that are increasingly proposed in great American cities, risk becoming vertical suburbs, whose residents and occupants are less likely to engage frequently and widely with the hurly-burly of city life.

Edward McMahon of the Urban Land Institute cuts to the chase, differentiating between density and high-rise buildings in his recent post for Citiwire, “Density Without Highrises?”. If the pendulum originally swung too far in the direction of sprawl over the past 50 years, the risk today is that it is swinging way too far back toward high-rise skyscrapers. "To oppose a high-rise building," he writes, "is to run the risk of being labeled a NIMBY, a dumb growth advocate, a Luddite — or worse. Buildings 20, 40, 60 even 100 stories tall are being proposed and built in low and mid-rise neighborhoods all over the world. All of these projects are justified with the explanation that if density is good, even more density is better."

Stop and think for a moment: What kind of environments spur new innovation, start-ups and high-tech industries? Can you name one instance, one, of this sort of creative destruction occurring in high-rise office or residential towers, in skyscraper districts? The answer is no. High-rise districts typically house either corporate office functions or residences. During the post-war era, while they were building these towers for their corporate functions, large U.S. companies housed their research scientists in green, low-rise R&D campuses, where the scientists could interact more freely.

America’s high-tech, venture-funded start-up model of innovation came of age not in skyscraper canyons but in places like Silicon Valley, which provided such an ideal eco-system for creativity because of its city-like aspects. As Jonah Lehrer told Cities recently, "Silicon Valley manages to replicate the essential function of a dense city, which is to foster a diversity of interactions and knowledge spillovers," albeit largely across industrial parks and based on the car.

Similarly, you don’t find great arts districts and music scenes in high-rise districts but in older, historic residential, industrial or warehousing districts such as New York’s Greenwich Village or Soho, or San Francisco’s Mission District, which were built before elevators enabled multi-story construction.

The urban tech districts that are emerging today, from SoMa in San Francisco to New York’s Silicon Alley and London’s Silicon Roundabout, are housed in similarly walkable, low to mid-story neighborhoods.

What we need are new measures of density that do not simply count how many people we can physically cram into a space but that accounts for how well the space is utilized, the kinds of interactions it facilitates. "By this measure," McMahon writes, "one block of an older neighborhood might include a community theatre, a coffee shop, an art gallery, two restaurants, a bicycle shop, 10 music rehearsal studios, a church, 20 apartments and a couple of bars, and all with much more 24/7 activity and intensity of use than one block of (much taller) office buildings on K Street [in Washington, D.C.]."

Too many people today conflate density with height. Real interactive density can be better achieved by other means. "Yes, we do need more compact, walkable higher density communities," writes McMahon. "But no we do not need to build thousands of look-a-like glass and steel skyscrapers to accomplish the goals of smart growth or sustainable development." Neighborhoods like Georgetown in Washington, D.C., Brooklyn’s Park Slope, and the Fan in Richmond were largely built before the age of elevators and they are all dense. New Orleans’ "French Quarter has a net density of 38 units per acre, Georgetown 22 units per acre." The real issue isn’t just height and the massing of people and work, but of enabling interaction and recombination.

"Density does not always demand high-rises," notes McMahon. "Skyscrapers are a dime a dozen in today’s world. Once a low rise city or town succumbs to high-rise mania, many more towers will follow, until the city becomes a carbon-copy of every other city in a 'geography of nowhere.'"

About the Author

Richard Florida is a co-founder and editor at large of CityLab and a senior editor at The Atlantic. He is a university professor in the University of Toronto’s School of Cities and Rotman School of Management, and a distinguished fellow at New York University’s Schack Institute of Real Estate.

These Bronx natives have been here for years. In the midst of rapid gentrification, they say they are taking control and offering the borough cultural experiences that as youngsters, they had to venture downtown to find.